Dual magnetron and circuits



Oct. 27, 1959 J. FORMAN DUAL MAGNETRON AND cmcuns Filed March 15-, 1956S N m T C 5 EE mm l E 9w 2 3 I MT l a m 6 T 2 4 D 1v N w 9 l w 3 2 M ILI 2 2 Ma fifi w m 2 M 7. 2 6 O 3 5 3 W Q 4 B 5 4 5 6 3 2 6 5 H a Q E l3 9. G 6 2. Wm mm M L E6 06 w m O M E INVENTOR.

JAN FORMAN OUTPUT SIGNAL ATTORNEY 2,910,651 r DUAL MAGNETRON ANDCIRCUITS.

Jan Forman, Malvern, Pa., assignor to BurroughsCorporation, Detroit,Mich., a corporation of Michigan This invention relates toelectronidtubes and more particularly relates to a compound magnetrontube in a coaxial arrangement and circuits therefor.

The electronic behavior of cylindrical magnetrons is well known, aspublished by A. W. Hull in Physical Review, vol. 18, p. 31, of 1921, andas shown and described in United States Patent No. 2,099,300 issued toK. Fritz entitled Oscillation Generator. With an elongated cathode, acoaxial, cylindrical anode structure and a magnetic field whose fluxlines permeate the tube parallel to the cathode, these tubes willoscillate in various modes depending upon the strengths of appliedmagnetic and electrical fields. Some modes have high-intensityoscillations while others are quite feeble. If a splitanode typemagnetron is used and a resonant circuit is connected between anodesegments of such a tube and the proper 'interelectrode voltage isapplied in relation to the magnetic field permeating the tube, the tubewill oscillate due to a negative resistance characteristic between itselements. In the production of these oscillations, electrons emittedfrom the cathode are accelerated to high kinetic energy and bombard theanode. Their kinetic energy is changed to heat when the electrons strikethe anode, and the anode can be raised to high temperatures through suchheating, with considerable efficiency in the energy conversion. f p

In most vacuum tubes, anode heating due to electron bombardment servesno good purpose,but rather contributes to lowered operating etficiencyand shortened tube life.

An object of this invention is to provide a novel cathode structure forall tubes requiring axial magnetic fields and novel circuit arrangementsfor such tubes.

Another object of this invention is to utilize a magnetron oscillator toprovide heat for the thermionic cathode of a surrounding magnetrondevice and simultaneously to provide alternating voltages useful inassociated apparatus.

Another object of this invention is to utilize a magnetron tubeoscillator to provide heat for a thermionic cathode and alternatingvoltage for simultaneous power supply and switching signals of a coaxialmagnetron beam switching tube.

Yet another object of this invention is to utilize a magnetron tubeoscillator to provide heat for a thermionic cathode of a surroundingmagnetron tube and simultaneously alternating voltages which may besynchronized with an applied signal to provide a useful output signal atthat frequency.

Still another object of this invention is to utilize oscillations of aninner magnetron to provide heat for the thermionic cathode of an outer,surrounding magnetron and simultaneously to provide alternating voltagesuseful in the associated apparatus or for radiation, and wherein thesurrounding magnetron oscillates at an independent frequency or at aharmonically related frequency, to provide complex waveforms in themixture of their respective outputs.

nitcd States Patent 9 7 2,910,651 Fatented Oct. 27, 1959 "ice Inaccordance with this invention a first, cylindrical anode magn'etron ispositioned in the center of a second, multiple-anode magnetron, with theouter surface of the cylindrical anode providing an emitting surface anda separate electron stream for the multiple anode magnetron, with asingle magnet providing the magnetic flux for both magnetrons; andwherein the resonant circuits connected to the first anode are used inaccordance with one phase of the invention to supply various operatingvoltages for the second magnetron.

For a more detailed description of this invention, reference is made tothe drawings in which:

Fig. 1A is a schematic circuit diagram of a dual magnetron andassociated circuitry embodying the invention;

Fig. 1B is a schematic diagram of typical circuit connections to eachspade and target electrode of a magnetron beam switching tube;

Fig. 1C is a schematic diagram of a continuous cylinder magnetronoscillator useful as the inner magnetron;

Fig. 2A is a schematic diagram of an embodiment of the invention forproducing operating voltages from the output circuit of the innermagnetron of the dual magne Fig. 2B is a schematic diagram of a circuitutilizing the inner magnetrons oscillations for radio transmission;

Fig. 3 is a schematic diagram of output circuits for a four-elementsplit anode inner magnetron;

Fig. 4 is a schematic diagram of an output circuit connected forsynchronization with an external signal; and

Fig. 5 is a schematic diagram of a further synchronizing circuitembodiment of the invention.

As shown in Fig. 1A, evacuated envelope 20 contains a dual magnetron.Targets 21, spades 22 and switching grids 23 are arranged to form thesuccession of beam forming and holding positions of a magnetron beamswitching tube. This arrangement of outer electrodes is described indetail in United States Patent No. 2,721,955 to Sin-pih Fan et -al.,entitled Multi-Position Beam Tube. Other configurations of outer anodestructure could be used within the scope of one phase'of this invention.Split anodes, and cavity resonators in a metallic block, as shown foranode structure 28 in Fig. 4,- are typical examples of alternate outeranode structures.

A cylindrical cathode 24-is provided for operation with the abovedescribed electrodes 21, 22 and 23. Cylinder 24 is of comparativelylarge diameter, and may be continuous, as shown in Fig. 1C, or splitaxially into a plurality of segments, as in Fig. 1A where cylinder 24 isshown split into segments 25 and 26.

While the outer surface of cylinder 24 is a cathode for one magnetronstructure, the inner surface of this cylinder is the anode for a secondmagnetron structure, coaxial to the first. Cathode 27 is a tubepositioned on the axis of cylinder 24, with a heater therein to raise itto electron emissive temperature. Electrons from cathode 27 can get nofurther than cylinder 24 because the gaps between segments 25 and 26 areexceedingly small and do not allow electrons to pass.

For magnetron type operation, a magnetic field permeates the dual tubestructure, with fiux lines substantially parallel to the axis thereof.This field is represented by the head-on view of flux arrow H in Fig.1A. Also, a positive voltage is applied to all targets 21 and spades 22through resistors 31' and 32 respectively as shown in Fig. 1B. Groundconnection 33 on the center tap of coil 35 keeps cylinder 24 at 'groundpotential relative to targets 21 and spades 22, to function as a cathodewhen heated to electron emissive temperature.

As shown in Fig. 10, the inner magnetron may be of the continuouscylinder anode type with oscillations between cathode and anode.

. bodiment is the split anode magnetron.

A voltage source such as battery 34 is connected between cathode 27 andsegments 25 and 26 of cylinder 24, to put cylinder 24 at a positivevoltage relative to cathode With cathode 27 heated to electron emisvetemp ra u e, a d it battery 34 pror j ii P Q -wn d ta e suit b e f ma stsn os s t s in e maa strqn t c re wi l t nsfe idsillatory e y t a conneted e o an uit u as h misdnator comprising coil 35 and capacitor 36.Other forms of resonator also can be used with the inner m agnetron,such as cavities within a thickened cylinder 24, Lecher i s. tc- Fo i -ape s l tqr t e m n tron presents a negative resistance across this tunedcirwin .o a a n tud dequa e fo .QYQ sQm ns p tive resistance of thetuned circuit and of other circuits coupled to it. As electrons movefrom cathode 27 to anode cylinder 24, they acquire kinetic energy. Thisenergy is transformed to heat when the electrons strike cylinder 24, andthe total electron flow in .this inner diode heats cylinder 24 to suchhigh temperatures that the outer surfaces of segments 25 and 26 becomeelectron emissive. The inner surface of cylinder 24 cannot contribute tothis emission since the cylinder encloses its own inner surface. Ifdesired, these outer surfaces can ,be ,coated with suitable electronemitters which provide more electron emission at lower temperatures thanplain metallic surfaces would provide.

Being electron emissive, theouter surface of cylinder 2.4 serves asacathode for the outer magnetron. When the outer magnetron device is amagnetron beam switching tube, the relationship between supply voltage+E on the targets and spades with respect to the cylinder 24 and themagnetic field H through .the tube must be such as to put the outermagnetron device well into its magnetron cut-ofi region. In general, thesupply voltages to the outer magnetron device must be such that, inconjunction with themagnetic field required by the inner magnetron, theouter magnetron may be operated satisfactorily. Operation of this outermagnetron, when it is a magnetron beamswitchingtube, is as described inthe above citedpatent. No'beam wilLform while the tube is in magnetroncut-oif conditionas described, until the potential on one of the spadeelectrodes 22 isdepressed to about half thenormal spadevvoltage. Then,theelectrons which have been orbitingiaroundthe cathode cylinder 24 butneverrcaching thespades 2 2 or target si, 21 will be confrontedby anegative voltage barrier in the cathode-to-spade-areamearest tothe lowervoltage spade. The electrons .are,diverte d;by this-barrier, tending toflow along an.equipotential line which leads then in between two spadesto strikethe target which covers this inter-spade space. This beam pathgrazes the lowervoltage spade, and some beam current flows to thatspade. This, current produces enough IR voltage drop through theresistor connecting the spade to itsvoltage supply +E .to hold the,spadesvoltage downto where the beam is held stably in that position.

A switching grid 23 also is in; the beam holding cavity defined by thelower-voltage spade, thenext spade and the target covering the gapbetween these spades. If this grid 23 is lowered in voltagebelow itsbias +V a voltage is reached at which the beam fans out toward thisswitching grid 23 and begins to strike the next spade, depressing it involtage from +E and causing the beam to advance to the next stableposition where it is held as described for the former position. Withsuccessive switching grids, driven toward a negative voltage in theproper sequence, the beam will continue to advance from one beam holdingposition to the next.

A suitable grid switching circuit is providedby common connections ofalternate grids which are driven througha push-pull or balanced circuit,asshown in Fig, 1A. When one set of alternate grids isdriven in thenegative direction and causes the beam toswitch, the other se of altenat -tgriqsawhish.includes.theisridiu the position to which the beam isswitching, is driven more positive so that the beams switching advancesonly one position in that half-cycle of the switching signal. On thenext half-cycle, another single position advance is made. 5

The previously described oscillations of the inner magnetron produces analternating current in coil 35. Coil 37 is coupled magnetically to coil35 and is connected through ring connectors 38 and 39 to sets ofalternate grids 23. The center tap on coil 37 is biased by voltage -[-Vfor proper switching and beam holding in tube 20. This couplingprovidesthe alternating voltage needed for the above-described.switching sequence of the outer magnetrons beam.

Fig. 2A shows a different circuit including secondary winding 40 coupledto coil 35 of the resonant circuit for the inner magnetron oscillator.Rectifiers 41 and 42 are connected to provide a full wave rectifier,developing a direct voltage from 'the center tap of coil 40 to theanodes of re'c'tiiie'rs 41 and 42. This voltage can be used toenergizethe spades and targets of the outer magnetrori by adding lead 45 forcathode connection and connecting lead 46 of Fig. 13 to the positiveterminal 47. Both secondary circuit 37. of Fig. 1A and 40 of Fig. 2Acould 'becoupled to the resonant circuit of one oscillator, thusproviding in one component both the spade and anode voltagejsupply andthe switching signal.

Fig. 2B shows another use for the alternating voltage provided by theinnerlmagnetron. When this magnetron is tuned to provide a highfrequency, the alternating voltage can be used as a radio carrier onantenna 30.

Fig. 3 shows a variation wherein cylinder 24 is split into 'foursegments 50, 51, 52 and 53. One pair of segments and 53 energizeresonant circuit 54, to which is coupled coil 55 toprovide the switchingsignals on grids :23 of an outer'magnetron as shown in Fig. 1. The otherpair of segments 51 and 52 energize resonant circuit 56, to which iscoupled coil 57. Coil 57 applies voltage to diodes 58 and 59 forming afull-wave rectifier. Capacitor 60 filters the oscillator frequency outof the rectified output. Further filtering circuits may be used ifdesired, but a simple capacitor provides adequate filtering when thefrequency is a radio frequency, due to itsvery low reactance to highfrequency. This direct currentoutputcantbe connectedto the supply leadfor all spades and targets, as described for Fig. 2. This innermagnetron is energized by'battery 34 and a heater for cathode 27. andoscillates as vpreviously described. Resonant circuits 5.4 and 56 mustbe tuned to the same fre quencyto enable oscillations in the illustratedcircuit.

In Fig. 3', the anode beating again is utilized to raise theoutersurfaces of segments50, 51, 52 and 53 to electronemissivetemperature, as a cathode for an outer magnetron. .Also,resonant circuitsf54 and 56 could be connected to opposite segments,rather than to adjacent segments as,shown, and function as an oscillatorwith equal orimproved quality of performance.

Fig. 4 sho ws a four segment split anode magnetron in which any pairofanode segments'supply a signal which can be utilized for any purpose,and the remaining two segments are,fed ,with a locking signal at afrequency to which therhaghettons oscillations are tobesynchronizedkesistorfil is. loading the resonant circuit 62 so astobroaden itsresponse for .ease of synchronizing through a, small band offrequencies within which the magnetron is tuned to oscillate-in anyevent. The anode heating is used to provide'a'cathode for an outermagnetron as previouslydescribed. r

Pig. 5 shows another. synchronized magnetron oscillator, except thatgrid wires 63 and 64 parallel to the axis receive, the synchronizingvoltage and split anode segments,,- 6 5 and. 66 are coupledto resonantcircuit 62. Oscillati ns. of this inner magnetron are synchronized byincoming signalson input transformer 67 applied to grid wires 63 and 64,and the resultant anodeheatin'g enables line sections, cavity resonatorsor ferromagnetic-cored inductances with suitable capacities also couldbe used. Pzor ultra-high frequencies and microwaves, the resonantcircuits can be within the tube envelope or be part of the envelope asin metal-ceramic tubes.

In Figs. 2, 3, 4 and 5 the collector and other electrodes of the outermagnetron are omitted in order to more clearly show and describe theinner magnetron, its circuitry, and use of its heating function toprovide a cathode for the outer magnetron and of its oscillations toprovide switching signals and D.C. supply for the outer magnetron.

What is claimed is:

1. A magnetron tube circuit including a magnetron tube comprising ananode structure, a first cathode coaxial to said anode structure, aplurality of electrodes parallel to and positioned concentrically aroundsaid cathode, the inner surface of said electrodes providing anodes forsaid first cathode and the outer surface thereof providing a cathodeassembly for said anode structure, and at least one resonantcircuitconnected to separate electrodes of said plurality of electrodes to tunethe oscillations between separate electrodes of said plurality ofelectrodes and to providea useful alternating output voltage.

2. A coaxial dual magnetron beam switching circuit comprising a centralcathode, a multiple segment cylindrical anode concentric about'saidcathode, a resonant circuit connected to a pair of said segments, avoltage supply connected to said resonant circuit and to said cathode toaccelerate electrons from said cathode to said cylindrical anode, anoutput circuit coupled to said resonant circuit, a cathode surface ontheouter surface of said multiplesegment cylindrical anode, a circulararray of spade electrodes concentric about said cathode surface,ajcircula r array of'target electrodes outside of said spade electrodesand covering the gap between successive spade electrodes, and switchinggrids on a circular locus intermediate between said spade and targetelectrodes and aligned with one edge of each spade electrode.

3. A coaxial dual magnetron beam switching circuit comprising a centralcathode, a multiple segment cylindrical anode concentric about saidcathode, a resonant circuit connected to a pair of said segments toestablish an oscillatory voltage between segments of said cylindricalanode, a voltage supply connected to said resonant circuit and to saidcathode to accelerate electrons from said cathode to said cylindricalanode, an output circuit coupled to said resonant circuit, a cathodesurface on the outer surface of said multiple segment cylindrical anode,a circular array of spade electrodes concentric about said cathodesurface, a circular array of target electrodes outside of said spadeelectrodes'and covering the gap between successive spade electrodes,switching grids on a circular locus intermediate between said spade andtarget electrodesand aligned withone edge of each spade electrode, inggrids in common connections of alternate grids and to said outputcircuit to utilize said oscillatory voltages to cause switching actionfor a beam in said circular arrays.

4. A coaxial dual magnetron beam switching circuit comprising a centralcathode, a multiple segment cylinand circuit means connecting saidswitchdrical anode concentric about said cathode, a first resonantcircuit connected to a first pair of said segments, a second resonantcircuit connected to a second pair of said segments, a voltage supplyconnected to said resonant circuits and to said cathode to accelerateelectrons from said cathode .to said cylindrical anode, output circuitscoupled to said resonant circuits, a cathode surface on the outersurface of said multiple segment cylindrical anode, a circular array ofspade electrodes concentric about said cathode surface, a circular arrayof target electrodes outside of and concentric to said spade electrodesand positioned along a circular locus to cover the gap betweensuccessive spade electrodes, and switching grids on a'circular locusintermediate between said spade and target electrodes and aligned withone edge of each spade electrode.

5. A composite magnetron tube and circuit comprising 7 a first magnetronincluding 'a central electron-emissive first cathode and a surroundingcoaxial electron-receiving anode, and a second magnetron including saidelectronreceiving anode as a second cathode and having an outerelectron-emissive surface, a plurality of electron receiving anodessurrounding and coaxial with said second cathode, means common to saidfirst and second magnetrons for providing a magnetic field therefor, andincluding a common resonant circuit coupled between said first andsecond magnetrons.

6. A magnetron circuit including a composite magnetron'tube comprising afirst magnetron including a central electron-emissive first cathode anda surrounding coaxial electron-receiving anode, a second magnetronincluding said electron-receiving anode as a second cathode and aplurality of groups of electron-receiving electrodes surrounding andcoaxial with said second cathode, said resonant circuit coupled betweensaid first magnetron and said switching electrodes of said secondmagnetron, and a magnet surrounding said first and second magnetrons andproviding an axial magnetic field therefor.

7. A coaxial dual magnetron beam switching circuit comprising a centralcathode, a multiple segment cylindrical anode concentric about saidcathode, a' resonant circuit connected to a pair of said segments, anoutput circuit coupled to said resonant circuit, a cathode surface onthe outer surface of said multiple segment cylindrical anode, a circulararray of spade electrodes concentric about said cathode surface, acircular array of target electrodes behind said spade electrodes andcovering the gap between successive spade electrodes, and switching gridelectrodes on a circular locus intermediate between said spade andtarget electrodes with each grid aligned with one edge of a spadeelectrode.

References Cited iii the file of this patent UNITED STATESPATENTS OTHERREFERENCES Beam Switching Tubesj; by Kuchinsky, 1955, 315-21. HayduBrohus Publication,

